The present invention relates to preparation of color image signals for display on a chromatophoric color display device.
A visual electronic display device consists of optical, mechanical, and electronic parts in an assembly that accepts data in an electronic form and provides a visual display of the data to an observer. In current society visual electronic displays are ubiquitous, being a requirement of every television set, every computer, and many dedicated products. Early display devices were limited to Black and White or monochrome. As color became available it quickly became the technology of choice. Of particular importance are color displays which possess a color gamut capable of reproducing the many hues, chromas, brightnesses and saturations of natural objects, which perform at television frame rates, and which address the needs of portable equipment, specifically in regards to battery power drain. There is also a particular need for displays that are viewable under very bright ambient conditions such as direct sunlight. Both of these needs are met by the inventive method presented herein when coupled with chromatophoric display device.
Electronic output display devices were popularized with the advent of television. Commonly images are presented at a rate of 30 frames per second. Each flame comprises two interlaced fields at 60 fields per second each as a means to reduce flicker. While television was initially in black and white, the development of color technology has made color the preferred approach. More recently a variety of displays have been developed and are under development. Many prior art displays are self luminous and the generation of light by the display itself or the inclusion of a dedicated light source is the major power need, the major source of waste heat, and for portable equipment, the major battery drain. An unavoidable result of a typical self-luminous display is brightness limitation. Under bright ambient conditions, as for instance outdoor sports events in broad daylight, a self-luminous display using a CRT or a liquid crystal display results in extremely poor visibility.
By contrast a chromatophoric display device is non self-luminous but utilizes ambient illumination. In this regard the chromatophoric display resembles a picture on a wall or in a magazine or an outdoor billboard. Brightness in reflected light replaces luminosity as a criterion.
This invention relates to, utilizes, and integrates a variety of technologies and disciplines, including:
CHROMATOPHORS
Chromatophore is the term used to designate selectable pigment elements to provide color selectivity in ambient illumination. The classical example is the color variation in certain animals, notably a chameleon, wherein changes of color are effected by means of pigment-bearing sacs. By analogy a chromatophoric display is a display wherein non self-luminous pixels change color and are viewable under ambient illumination. A first primary benefit of a chromatophoric display is that the display power supply need not provide illumination power. This is significant for portable display devices wherein power must be supplied by a battery pack. A second primary benefit is that the display is viewable under very bright conditions, such as direct sunlight. The utilization of CRT or other self-luminous displays in high ambient light environments is often disappointing in that there is insufficient illumination for viewing. By contrast, however, an out door sign such as a billboard is highly visible in bright sunlight. A chromatophoric display combines aspects of a painting hanging on a wall or an outdoor sign viewed in reflected light with the moving features of cinema or television. Like a picture on a wall it utilizes and requires ambient illumination for viewing.
The present inventive method provides means to transform RBG color signals as intended for color television or a color computer display into signals useful in chromatophoric displays.
Two of my patents/applications for chromatophoric displays have applicability and are incorporated herein by reference. The first U.S. Pat. No. 6,081,249 titled "WRAP AROUND MEMBRANE COLOR DISPLAY DEVICE" issued Jun. 27, 2000. The second titled "ROLLER OPTICAL GATE DISPLAY" has been declared "special" in view of the inventors age being over 65 years. This is identified as Ser. No. 09/336,802 (attorneys docket EDH/99001 submitted Jun. 11, 1999).
Color Science:
It has been demonstrated by prior art, in both xerography and offset printing that with black, cyan, magenta and yellow (CMY) dyes or pigments a full color palette is available. The additional colors of, red green and blue (RGB) can be made available either as separate toners or by dye-on-dye using the CMY toners.
The following color definitions are common in the industry and are incorporated herein:
BRIGHTNESS: Perceived quantity of visual flux. PA0 HUE: Visual sensation to which an area appears to be similar to one of a set of standard colors, or combinations of these. PA0 SATURATION: The colorfulness of an area judged in proportion to its brightness. PA0 CHROMA: Colorfulness of an area judged as a proportion to brightness of a similarly illuminated area that appears White. PA0 GAMUT: The three-dimensional color space that encompasses all of the colors reproducible by the process. PA0 PALETTE: Specific colors available within the gamut.
Full color capability will include means to produce brightnesses, hues, saturations, and chromas of natural objects and scenes.
Color dye and pigment materials are in an advanced state of technology as a result of ink development in the printing industry, and toner development for color xerography. Pigments and dyes for the highlight colors of Cyan, Magenta and Yellow are capable of rendering highlight colors found in nature with high brightness and high fidelity. Relative to White the brightnesses of these highlight materials are equal to a shade of light gray. Pigments for the darker colors of Red, Green and Blue can be selected equivalent to the brightness of a dark shade of gray. These shades along with Black allow four levels of brightness for each pixel and a wide range of brightnesses are available for groups of neighboring pixels.
The human eye perceives color at a resolution significantly lower than its perception of brightness. If a display is configured to match brightness resolution to the capability of human vision then color of individual pixels is not resolved visually but will merge with adjacent color pixels into intermediate values of hue and chroma. As a result of this feature of human vision a very large number of hues and chromas can be made available from the eight basic primary colors at the same time high resolution in brightness is achieved. Because of this, a large color palette is obtainable with just eight common primary colors Black, Red, Green, Blue, Cyan, Magenta, Yellow, and White (KRGBCMYW). In the development of color television advantage was taken of the limitations of visual color resolution in expanding the early monochrome television to include color. The limited bandwidth required for color allowed color signals to be placed in unused potions of the spectra without requiring an increase in transmission bandwidth.
In self luminous displays, as for example a cathode ray tube, adequate color rendition can be achieved by employing Red, Green, and Blue patches in a localized group utilizing brightness control. In the case of reflective chromatophoric displays, however, the rendition of color highlights in a given area demand that all pixels in the area be of bright highlight color. Both the bright colors of Cyan, Magenta and Yellow and the darker colors of Red, Green and Blue, along with White and Black are needed to develop a full gamut.
A chromatophoric color display possesses the inherent capability for all pixels in any given area to be any of the bright primary colors, Cyan, Magenta, and Yellow. This capability allows the display of highlight colors in maximum brightness.
Where self-luminous displays are commonly characterized in terms of luminosity, chromatophoric displays must be characterized in terms of brightness.
Flicker is common in displays that rely on a phosphor since the phosphor for any given pixel is stimulated once only for each frame and the luminosity decays over the rest of the frame. In cinema flicker results from the limited fraction of time that the film gate is open during a frame time. A cinema frame is mostly all on when the film gate is open and mostly all off when the film gate is closed. By contrast in a chromatophoric display pixels once set remain fixed for an entire frame time, until reset in the following frame. Pixels in a frame are changed in sequence one at a time. Pixel brightness does not decay as in the case of the phosphor on a CRT. At no time is the frame completely Black as is the case between frames in cinema. As a consequence flicker in a chromatophoric display will be minimal or non-existent. Psycho-somatic effects induced by flicker as experienced by certain individuals will likewise be minimal or non-existent.
It is an object of this invention to provide a method for the transformation of Red, Green and Blue television and/or computer display signals into signals suitable for display on a chromatophoric color display.
It is a further object of this invention is to include in said transformation method means to preserve spatial resolution in luminosity as spatial resolution in brightness for a chromatophoric display.
It is another object of this invention to include in said transformation method the means to preserve the color qualities of brightness, hue, saturation and chroma of signals intended for a self-luminous display when transformed into signals for a chromatophoric color display.
It is an additional object of this invention to include in said transformation method means to perform the transformation at frame rates and pixel densities compatible with state of the art television and/or computer displays.
It is yet another object of this to provide a transformation method wherein advantage is taken of selected light pigment shades together with selected dark pigment shades for brightness control.
It as a further object of this invention to include in said transformation method means to enable the utilization of available pigments and/or dye materials in a chromatophoric color display.
It is still another object of this invention to provide an enabling means to implement chromatophoric displays that are nearly flicker free, that possess high visibility in high ambient light environments and wherein power is not required to generate display illumination.